Concerns about propranolol side effects

Its a beta-blocker im taking as needed for severe anxiety. Ive had none it made me feel fearless it was nice after having sudden spontaneous severe anxiety attacks that made me freeze up and would last for several hrs the worst one was last week and lasted 6 hrs. I took it at the onset of one after i recived my med delivery 3 days ago and it stoped it after 20 min and the beta-blocker lasted about 6 hrs. Long enough for me to go to bed. Its been a life saver.